Milo g



(No Model.)

M.G .KELLOGG. MULTIPLE SWITGHBOARD.

Patented Oct. 26,1897.

s s wwu mm m? m? Line fifa loop-plug and, when a plug is inserted, to

N Tnn STATES PATENT Tries.

MILO G. KELLOGG, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE KELLOGGS\VITCIIBOARD AND SUPPLY COMPANY, OF SAME PLACE.

MULTIPLE SWITCHBOARD.

SPECIFICATION forming part of Letters Patent No. 592,385, dated October26, 1897.

Application filed August 5, 1890.

To all whom, it 11mg concern:

Be it known that l, MILO G. KELLOGG, of Chicago, in the county of Cookand State of Illinois, temporarily residing atStuttgart, in the Empireof Germany, have invented certain new and useful Improvements inMultiple Switchboards for Telephone-Exchanges, of which the following isa full, clear, concise, and exact description, reference being had tothe accompanying drawings, forming a part of this specification.

My invention relates to a telephoneexchange system in which the linesare singlecircuit lines grounded at their outer ends and normallygrounded at the central office; and it consists in a system of testingthe lines to determine whether they are in use.

In the drawings illustrating my invention, Figures 1 and 1 representsections of two multiple switchboards of the exchange to which the samelines are connected. Fig. 2 shows a diagram of the boards with themainline apparatus and connections necessary to illustrate my invention.Fig. 3 shows a diagram of an operators cord system to be used inconnection with the boards. Fig. t shows an operators test system to beused at the board. Fi 5 shows a subscribers-station apparatus.

In Fig. 2, A is a sectional View of the switchboard shown in Fig. 1, andA is a sectional View of the switchboard shown in Fig. 1", each asindicated by the line (1 e.

I place as many boards in the central oflice as are found necessary ordesirable in order to properly operate the exchange. On each board is aspring-jack or other suitable switch for each line. Each switch has acontactspring which normally connects with an insulated contact-pieceand is adapted to receive disconnect the spring'from the contact-pieceand connect the two contact-pieces of the plug with the spring and saidinsulated contactpiece, respectively. The switch is also adapted toreceive a singlecontact switch-plug and, when a plug is inserted, todisconnect the spring from the contact-piece and connect the spring withthe contactpiece of the plug.

In the construction of the switches as shown and as will hereinafter bedescribed I Serial No. 361,112. (No model.)

prefer to have a contact-point electrically connected with thecontact-piece and on which the spring normally bears, as there is lesschance of poor connection when the spring bears 011 a point than when itbears on a surface adapted to be brought into connection with theplug-contacts.

In Fig. 2, g 9 represent the springs of the different switches, it h thecontact-points, on which the springs normally bear, and jj thecontact-pieces of the switches,connected with the points h h. Z l arethe switch-holes. a Z) are the rubber strips; on which the metal partsof the switches are mounted, as shown, and through the fronts of whichare the switch-holes Z Z. The contact-pieces jj are so placed along oneof the surfaces of the plugholes as readily to form connection with oneof the contact-pieces of the loop-plugs. The

holesl Zare adapted to receive the switchplugs shown in Fig. 3 andmarked D D, and when a plug is inserted into a switch it raises thespring 9 from the contact-point h, and the spring g and thecontact-piece of the plug are in contact. These holes are also adaptedto receive the loop-plug shown in Fig. 4, and when a plug is insertedinto a hole it raises the spring of the switch from the contactpointh,and the spring 9 and the contact-piece j of the switch are in contactwith the two contact-pieces of the plug, respectively.

WV and X are calling-annunciators, one for each of the lines shown. Eachannunciator has a pair of contact-points normally (or when theannunciator does not indicate a call) in contact with each other, butwhich are separated by the annunciator while it indicates a call. Thetwo contact-points of a pair are marked 19 and g, respectively. One ofthem, q, is a spring-contact which is pressed by the annunciator-dropwhen the drop falls away from its corresponding contact-point p. Thecontact-point p is represented as an anglepiece which passes over thespring q and is in contact with the spring when the springis notactuated by the annunciator-drop.

B is a test-battery placed in the common ground wire or connection ofthe lines.

Two lines are shown in the drawings, one marked line No. 1 and the otherline No. 2. These lines are ordinary single-circuit lines In theoperators cord system shown in Fig.

3, DD are the switch-plugs of a pair of cords. n are the rubberinsulations of the plugs, and 'm 'm are their contact-pieces. Thesecontact-pieces pass each to the bottom of its plug and are adapted torest normally, or

when the plug is not in use, onthe metal piece 0, which then connects itwith the ground. Weights, as is usual, or similar devices may be used tobring the contact-pieces of the plugs into contact with the piece 0 andsecure a good connection. These plugs are adapted to be inserted intoany of the switches at their board, and when a plug is inserted itoperates the switch, as above described. should be inserted, so that thecontact-piece m is in contactwith the spring g. The connections of thelines might have been reversed, so that the lines pass first to thecontact-piece j of each of their switches, and in that case the plugsshould be inserted in such a position that their contact-pieces formconnection with the pieces j of the switches. Y

.is the looping=in switch for the pair of cords shown. K is thecalling-key, and i2 is a clearing-out annunciator. t is the operatorstelephone,- and B is her calling generator or battery. The circuits aresu bstantially as shown.

The operation of the system in connection with the switchboards will beapparent to those skilled in the art. It will readily be apparent thatwhen a line is switched by the insertion of a plug into its switch theline is disconnected from its normal groundwire at the central office inwhich is the testbattery B and is connected into a circuit with the pairof cords. Only one pair of cords is shown,but the connection of suchother pairs, with their accompanying apparat-us as the operator mayneed, will be apparent to those skilled in the art. To each pair ofcords with its plugs belong aloopingin switch, a clearing-outannunciator, and a calling-key. One telephone and one callinggeneratorwill answer for her system of cords.

In the operators test system shown in Fig. 4, T is a loop test-plugadapted to be inserted into any of the switches and, when inserted, tooperate them as heretofore described, and S is a test receivinginstrument. The instrument is connected in a loop which terminates inthe two contact-pieces of the plug. Each operator has one cord systemand one test system and they are conveniently mounted and arranged forher work.

The plugs switched to.

In thesubscribers-station apparatus shown in Fig. 5, 1 is thetelephone-switch. 2 is the calling-generator. 3 is the signal-receivingbell. 4. is the subscribers telephone. 5 is the secondary, and 6 is theprimary, of the induction-coil. 7 is the transmitter. 8 is thetransmitter-battery. 9 is a condenser. These parts may be of usual formsof apparatus and are connected as shown or in other ways,

. so as to perform practically the operations required and theoperations hereinafter described.

When the subscribers telephone is on its switch, the signal-receivingbell is in the circuit of the line, and. the telephone, the secondary ofthe induction-coil, and the condenser are shunted by awire of smallresistance, so as to be practically out of the circuit. When thetelephone is off the switch, the telephone, the secondary of theinduction-coil,

.and the condenser are in the circuit and the signal-bell is'praeticallyout of the circuit.

The test receiving instruments and testbatteries should be soconstructed and adjusted to each other and the circuits that theinstrument will sound or'respond when it and the battery are looped intothe closed circuit of any single line and the subscribers telephone isnot off its switch for use, but will not respond if the circuit is openat any point, or if the subscribers telephone is off its switch and thecondenser at the subscribers station is included in the circuit, or theline is switched with another line and thereby has its test circuitopen, as will hereinafter be indicated.

The operation of the test system is as follows: When an operator desiresto test a line,

she places her test-pluginto the switch of the line and by so doingdisconnects the points g and h of the switch and connects them with thecontact-pieces of the plug. If, then, the line is not switched at anyboard and the annunciator does not indicate a call and the subscriberstelephone is on its switch, the testreceiving instrument will sound orrespond, indicating that the line is free to be If, however, the linenot being switched, the subscriber has sent ina call and the annunciatorindicates the call or has taken his telephone from the switch for use,the instrument will not sound, as the line being open at theannunciator-points or the condenser in the circuit will prevent it fromdoing so. If, again, the line is switched at some board and the test ismade in the cutoff portion of the line--that is, that portion which isbetween the switch used for switching and the oflice grouud'theinstrument will not sound because the test-circuit is open at the pairof contact-points of the switch used for switching. If, again, the lineis switched at any board with another line and the test is made in someswitch between the one used for switching and the subscribers station,the instrument will not sound on account of the battery being cut offfrom the circuit in which IIO the test receiving instrument is included.When a test of a line is made and the test receiving instrument sounds,the operator knows that neither the line nor the operators telephone isswitched for use nor the line-annunciator indicates a call, and when theinstrument does not sound she knows that either the annunciatorindicates a call or the subscribers telephone is switched for use or theline is switched for use, and she will not connect the line with anyother line. By this system a subscribers line is reserved to himselffrom the time he sends in his call or takes the telephone down for use.

In multipleswitchboard systems an operator to whom certain lines areassigned to answer frequently receives several calls at practically thesame moment and it may re quire some time before she can switch to acertain line and answer its call. In systems in which the test dependsonly on the line being switched at some board another operator may inthe meantime test the line and, finding it to test free, may switch itwith another line and cause annoyance and confusion to the subscriber.This cannot occur in this system of testing because as soon as thesubscriber takes his telephone from its switch the line will test busywhether or not it is switched at the central oflice. Again, in systemsof testing which depend only on the subscribers telephone being on oroff its switch confusion frequently arises from the fact that asubscriber places his telephone on its switch when he is throughconversation without sending in a clearing-out signal, and his linetests free and is connected to when it is already switched with anotherline. Lines in this condition are technically called tied up. This,again, cannot occur in this system because the line will test busy untilis disconnected at the central office whether not the subscriberstelephone is on its vitch. The system, therefore, combines the dvantagesand obviates the disadvantages of the two general systems of testingoutlined above. Moreover, in this system the line tests busy as soon asthe calling-generator operates and the annunciator indicates a callwhether the subscriber may have taken down his telephone for use or havereplaced it on its switch.

I claim as my invention and desire to secure by Letters Patent 1. Ina-telephone-exehange system, a telephone-line normally on closed circuitand containing a test-battery in its circuit, in combination with anannunciator normally in the circuit of the line, having contact-pointsby which the circuit is open while the annunciator indicates a call, asubscribers-st-ation apparatus containing a telephone, atelephone'switch, a condenser, contacts and connections by which thecondenser. is included in the circuit of the line while the telephone isswitched for use and only then, a test receiving instrument and switchapparatus for looping the same into such normally closed circuit, saidinstrument being constructed and adjusted to sound or respond whenlooped into such circuit and neither the telephone is switched for usenor the annunciator indi cates a call, and not to sound or respond wheneither the annunciator indicates a call or the telephone is switched,substantially as set forth.

2. In a telephone -exchange system, telephone-lines normally on closedcircuit and each having a test-battery in circuit, in combination withan annunciator normally in the circuit of each line, with contact-pointsby which the line'cireuit is open when the annun ciator indicates acall, a subscribers-station apparatus for each line, containing atelephone, a telephone-switch, a condenser, contacts and connections bywhich the condenser is included in the circuit of the line when thesubscribers telephone is switched for use and only then, a testreceiving instrument and switch apparatus for looping the same into thenormally closed circuit of either line, said instrument beingconstructed and adjusted to sound or respond when looped into theline-circuit and neither the telephone is switched for use nor theannunciator indicates a call and not to sound or respond when either thetelephone is switched or the annunciator indicates, substantially as setforth.

3. In a telephone exchange system, groundcircuit lines normally onclosed circuit and containing a test-battery in their commonground-wire, in combination with an annunciator normally in the circuitof each line, each annunciator having a pair of contactpoints by whichits line-circuit is open while it indicates a call, asubscribers-station apparatus for each line, containing a telephone, atelephone-switch, a condenser, contacts and connections by which thecondenser is included in the circuit of its line while the subscriberstelephone is switched for use and only then, a test receiving instrumentand switch apparatus for looping the same into the normally closedcircuit of any line, said instrument being constructed and adjusted tosound when looped into the circuit and neither the subscribers telephoneis switched for use nor the annunciator indicates a call and not tosound when either the telephone is thus switched or the annunciator thusindicates, substantially as set forth.

. 4. In a telephone-exchange system, a telephone-line normally on closedcircuit, in combination with an annunciator normally in the circuit ofthe line, having contact-points by which the circuit is open while theannunciator indicates a call, the subscribefs-station apparatuscontaining a telephone, a telephone -switch, a condenser, contactpointsand connections by which the condenser is included in the circuit of theline while the telephone is switched for use and only then,

IIO

a test receiving in strument, switching apparatus for looping the sameinto the normal circuit of the lineand a test-battery in the circuitthereby established, said instrument being so constructed and adjustedas to sound or respond when included in such circuit and neither thetelephone is switched for use nor the ann'unciator indicates a call andnot to sound when either the telephone is thus switched or theannunciator thus indicates, substantially as set forth.

- 5. In a telephone-exchange system, telephone-lines grounded at theirouter ends and multiple switchboards for the same, each board containinga switch for each line, each switch having a pair of contact-pointsnormally in contact, adapted to receive a switchplug and when the plugis inserted into the switch to have the pair of contact-points of theswitch separated and the contact-piece of the plug in contact with theline contactpoint of the switch, and adapted to receive a loop test-plugand when the plug is inserted into the switch to have the pair ofcontactpointsvof the switch separated and connec- Switch to the ground,in combination with an annunciator normally in the circuit of each line,each annunciator having a pair of contact-points by which its circuit isopen while it indicates a call, a test-battery normally in circuit witheach line, a subscribers-station apparatus for each line, containing atelephone, a telephone-switch, a condenser, contact-points andconnections by which the condenser is included in the circuit of theline while the subscribers telephone is switched for use and only then,and a test receiving instrument at each board, included in aloop the twoends of which terminate in the two contact-pieces of a loop test-plug,each instrument being constructed and adjusted to sound or respond whenit is included in the normal circuit of either line and neither the linenor its subscribers telephone is switched for use nor the annunciatorindicates a call and not to sound when either the line or the telephoneis thus switched or the annunciator thus indicates, substantially as setforth.

In witness whereof I hereunto subscribe my name this 23d day of June,1890.

MILO G. KELLOGG.

\Vitnesses:

EMIL ABENHEIM, ABBOTT L. MILLS.

